What is encryption?

The word "encrypt" means to hide, or to make secret. The earliest forms of cryptography (which just means "secret writing") used simple ciphers to turn ordinary text into unreadable nonsense.

For example, suppose you wanted to encrypt a phrase in such a way that your friends could easily read it, but others could not. You would need to have a simple rule, or ciphering algorithm, that could be used to both encrypt and decrypt the message. A simple encryption algorithm is "shift each letter by one." With this simple code, "a" is coded as "b" and so forth.

If you try a short example yourself, it should be obvious that computers make the process of encryption and decryption easier and faster.

The "shift each letter by one" cipher is easy to implement - it is also easy to figure out. Over time, more complex encryption algorithms have been used to make it more difficult for others to figure out what cipher is being used.

Keep in mind that a cipher can be made to work on any set of "bits" - not just text. It is also possible to encrypt a digital picture file, a digital music file or a digital video file. Once such a file has been encrypted, it must be decrypted to be viewed or heard.

If you are really serious about security, you will want to use a really serious encryption standard. See the Data Encryption Standard (used by the federal government for over thirty years) or the Advanced Encryption Standard (the current gold standard for encryption).